The present invention relates to a surgical instrument which comprises, inter alia, a tool for screwing in a surgical implant or for cutting a thread in human bone tissue with thread tap. Also included is a unit for supplying power and controlling the speed of an electric motor included in the tool, and detection and display members, the detection members transmitting signals, dependent on the torque and torsional angle of the tool, to the display members. The latter comprise a computer unit, for example a microprocessor, with associated display and memory members, which respectively display and store a torque curve effected by the tool on the basis of the screwing-in or thread-cutting. This curve shows the torque as a function of the torsional angle. The display member can in this case be of the type which comprises a computer screen, VDU, etc. The invention also relates to an arrangement in which the above surgical instrument is included.
It is already known, for example from PCT publication WO 95/20146, to use, in screwing tools, a unit for supplying power to an electric motor. An amplifier is connected to the current supply circuit of the electric motor, and this amplifier is followed by an analog/digital converter. The latter is in turn connected to a computer unit with VDU. It is also already known per se to investigate various bone qualities of the human body and to draw up statistics on these bone qualities. In this case it is possible to detect the capacity of a particular tool to penetrate the respective bone/bone tissue, and to relate the penetration capacity to the bone quality. It is also known to use torque-controlled tools for screwing and thread-cutting in conjunction with dental work using implants, dental bridge structures, etc. Different evaluations of bone quality for different persons of different ages are known per se.
There is a need for effective means for aiding surgeons, dentists and equivalent personnel performing advanced dental work. For example, when cutting a thread and fitting a screw, the surgeon or equivalent person must have complete control of the work being carried out. The implant and dental structure in question must be applied optimally. This optimal application is to a large extent dependent on the quality of the bone tissue in each individual case, which quality is not always entirely apparent from external inspection. Hitherto, a good result has been associated with professional skill and experience. The present invention solves the problem by indicating with great precision, for example, the bone quality, strength of the screw material, etc.
When drawing up statistics and other information, it is important to be able, in a simple manner, to document the respective work performed in respect of bone quality, patient type, age, type of structure, implant application, etc. The invention solves this problem too.
It is also important that the operating function of the tool in question can be given a simple and well proven function and component design. The invention solves these problems too. The invention uses the fact that the torsional angle is known.
The feature which can principally be regarded as characterizing a surgical instrument according to the invention is that the detection member or the detection members transmit(s) signals, dependent on the torque and angle position(s) of the tool, to the display members which comprise a computer unit which, besides the display member, has memory members, and that the display member is arranged in this case to display a torque/torsional angle curve, which forms the basis for assessing the quality of the implant/bone tissue.
In one embodiment, the unit for supplying power and controlling the speed is arranged to provide the electric motor with an essentially constant speed of rotation or a known variable speed of rotation.
With the torque/torsional angle curve it is also possible to check if the screw material is of good quality and that the elasticity limits in question are not being exceeded. The said storage member/members is/are arranged to store one or more torque curves which can be related to different screwing-in and/or thread-cutting cases.
In one embodiment, the detection member comprises an amplifier and, connected-in downstream of this, an analog/digital converter which converts the signals of the detection member into corresponding data signals. The said data signals are shown, with the aid of low-pass filtering, as a histogram on the display member""s screen, where each column corresponds to a number of mean values of the torque in order that rapid variations or ripples will not disturb production.
The arrangement according to the invention is characterized essentially in that detection members detect torque(s) effected by the tool and relate this to the torsional angle position or torsional angle positions, and in that a display member or display members is/are arranged to display a curve which shows the torque variation as a function of the torsional angle position, and in that the display member/members comprises/comprise or is/are connected to one or more storage members. Further characteristics are that the arrangement also comprises an evaluation system for bone quality, statistics on bone qualities, etc., and that the said storage member/members is/are arranged to store one or more torque/torsional angle curves. The stored curves are further arranged such that they can be transferred to the evaluation system.
In a preferred embodiment, a removable storage member is used as storage member. The storage member can here have the form of a card which can be loaded with data (cf. credit card, electronic wallet card, etc.). The respective curve formation for one or more patients is fed into the card in question. After the data information has been loaded, the card can be removed for use, i.e. insertion, in the evaluation system.
With the above functions built into a surgical instrument, which additionally has facilities for cooling, speed control, direction of rotation control, torque control, etc., a very attractive technical support instrument for the surgeon or equivalent is obtained.